Hello, I have been using unraid for ~3 years and have constantly been struggling with iowait. I recently changed my cpu to a i5 13400 in hopes of it fixing my issue but it did not. It is also paired with 32GB DDR5 5200MHz.

 

When downloading a large file to the pool, which is setup on a exclusive share, I still get iowait errors and the speed going up and down(sometimes even dipping to around 0) on repeat.

 

The zfs pool(raid0) consists of x2 Kingston KC3000 M.2 NVMe SSD Gen 4 2048GB and x1 samsung tb ssd

 

Edited December 4, 20241 yr by tetamo

One of the SSDs is a QLC flash device, it will be much slower than the other two.

16 minutes ago, JorgeB said:

One of the SSDs is a QLC flash device, it will be much slower than the other two.

That is true, but should it really affect the pool this hard? That downloading a single torrent causes it iowait all the time?

QLC can be extremely slow after the pseudo SLC cache is exhausted.

Just for giggles, if you can afford the time and space, I would re-create your cache pool with the two identical kingston NVME drives and leave out the Sata SSD as it's about 15x slower. (7000MB/s vs 500MB/s)

28 minutes ago, MowMdown said:

Just for giggles, if you can afford the time and space, I would re-create your cache pool with the two identical kingston NVME drives and leave out the Sata SSD as it's about 15x slower. (7000MB/s vs 500MB/s)

Yeah I know the drive is way slower, i just picked up the fast drives as they were pretty cheap during black week but i really needed extra 2tb. I'll probably just order another nvme and remake the pool

2 hours ago, MowMdown said:

500MB/s)

And after the pseudo cache is exhausted, writes will be limited to 160MB for that device